Community composting can be performed all year long, but the hard freezes encountered in colder climates pose special challenges. It may be that winter composting is limited to stockpiling frozen kitchen scraps for later incorporation after spring thaws. Decomposition slows down considerably at the lowest temperatures and may stop completely, but frozen material will “ripen” upon thawing and create more surface area for the active composting process to begin when mixed back in with a good brown source in the spring.
You can winterize a compost bin in a number of different ways. Stacking bales of hay around the perimeter of a square or rectangular bin may provide sufficient insulation to keep pile temperatures moderate through all but the coldest winters. Old carpet remnants, blankets, or stacks of cardboard may also help, if added to buffer the tops of open piles or bins from hard frosts. Lining the interior walls of pallet-based bins or other porous structures with large sheets of cardboard may also help to retain some warmth and ensure continued bacterial activity.
One strategy for winterizing a compost site borrows from household composting practice in simply planning on the deep freeze ahead. Make sure your site goes into November with 2 to 3 empty bins available for winter stockpiling. Partially composted material – much of it trimmings or entire withered plants from the garden – will be fairly dry and will not present odor problems or attract vermin. You can make a separate resting pile for this material and either distribute it to garden beds for sheet composting over the winter or leave as a larger windrow to rot down at a later date. The key is to plan ahead and enter the winter months with a backup option for storing accumulating, but frozen and largely inert, material for spring composting.